Selectable dual mode triggers for semiautomatic firearms are known, which include triggers capable of actuating and firing rounds on both pull and release of the trigger. Examples of such systems are disclosed in U.S. Pat. No. 8,667,881 B1 to Hawbaker, granted 2014 Mar. 11 (herein “the '881 Patent”), and U.S. Pat. No. 8,820,211 B1 to Hawbaker, granted 2014 Sep. 2 (herein “the '211 Patent”) (collectively “the Hawbaker patents”), both of which are incorporated herein by reference. The characteristics of selecting modes of actuation in which only one round is discharged with one function of the trigger was approved by the ATF and granted the patents mentioned above and incorporated herein.
The introduction of a trigger that actuates on both pull and release presents several challenges. During the testing of this new trigger, misfires were sometimes experienced due to light primer strikes, unexpected trigger states during actuation, and magazine changes. It quickly became apparent that improvements were needed to address these and related issues.
For example, it became apparent that there needed to be a mechanism added to the trigger that would ensure that the carrier is seated before the trigger is actuated, so that the anti-hammer-follow-disconnect does not engage out of sequence and so that the firearm could be placed in safe mode (safety on) at any time. The mechanism would need to ensure activities occur in the proper sequence and that the trigger and firearm are ready for the next desired function to occur. The addition of a special automatic trigger lock (sometimes referred to as a “timing lever” in the '807 Application) as described in the '460 Application ensured that the sequence of events is maintained in the proper relationship, eliminating misfires, jams and out-of-battery discharge. While that trigger lock was intended to control the sequence of activities, it became apparent during subsequent testing that intermittent failures were still occurring. In working to solve these problems, innovations were discovered that have applicability to not only pull-and-release triggers, but also to firearms generally.